AHC issues with SPC uppers. (1 Viewer)

[OwnerCS]

I've been wrestling with ACH ever since I installed SPC uppers. I'm reaching the end of my rope fairly quickly. I have PADDOs instruction printed and in the garage. by the truck. I've been through the procedure.

The front it at 22" from the wheel center. I have released the torsion bars to the point of being uncomfortable with the amount of looseness. I cannot get the front to drop to spec.

If I move the sensor, nothing happens with hight. Only the sensor values on Techstream change.

I just want to show that the AHC sensor is shoved all the way up in the slider at full droop with washers stacked under the bracket to get it up high enough to clear.

Has anyone been able to successfully use ACH wtih SPC uppers?

 

[hoser]

Try the other direction.... as in lower the upper bolt.

 

[OwnerCS]

Try the other direction.... as in lower the upper bolt.

Thanks. Will give it a shot tomorrow.

 

[1sar39]

I ran SPC with AHC without any problems. I was running the sensor linkage at the top of slider with oem uca's, and I think my hub center to fender was around 21 1/4". To get the same 21 1/4" with the SPC uca, I was running the linkage around the middle of the slider.

You could be asking too much from the sensor with the washer stack, and it looks like you shortened your sensor linkage, too. Try what hoser said and lower the sensor linkage.

Oh yeah, I bent the slider tab away from the uca for clearance. Worked fine for me.

 

[LndXrsr]

In theory, your new UCAs shouldn’t change anything about the height and/or sensor readings. I know in practice that may be different, but I’d suspect faulty height sensors or some sensor adjustment goofiness as your root cause.

 

[Ramathorn15]

Based on the washers and position on the arms, it does seem you're adjusting in the wrong direction. It can be confusing. To lower the suspension in N, you want the height sensor arm to travel down and away from the control arm, not up.

The way I think about it is this: the truck is going to try to keep the sensor arm in the same position by adjusting the suspension. If you shorten the distance between the sensor arm and the control arm, the truck is going to raise itself to return the sensor arm to the normal position. The opposite for lowering the truck.

 

[OwnerCS]

Based on the washers and position on the arms, it does seem you're adjusting in the wrong direction. It can be confusing. To lower the suspension in N, you want the height sensor arm to travel down and away from the control arm, not up.

The way I think about it is this: the truck is going to try to keep the sensor arm in the same position by adjusting the suspension. If you shorten the distance between the sensor arm and the control arm, the truck is going to raise itself to return the sensor arm to the normal position. The opposite for lowering the truck.

Excellent point. I'm going to give it another try this afternoon.

 

[OwnerCS]

During the weekend I moved the sensor arm position in the slider up from full up to full down. No change in the front lift while moving the sensor arms up or down.

Just looking back on some previous TechStream captures, I think the problem may be with the rear. These captures from last week and February.


Code 1762 with accumulator and rear pressur pressure sensors on zero.

February

July 6 - Before adjusting torsion bars.

 

[LndXrsr]

Moving N to L to N a few times never gets you rear or accumulator readings? You can try to disconnect the AHC temp sensor plug from the pump, that sometimes gets the rear pressure to pop up. But no accumulator pressure reading suggests an issue with Techstream or the AHC circuitry. Could also be the source of your height issues if that's the case.

 

[OwnerCS]

Moving N to L to N a few times never gets you rear or accumulator readings? You can try to disconnect the AHC temp sensor plug from the pump, that sometimes gets the rear pressure to pop up. But no accumulator pressure reading suggests an issue with Techstream or the AHC circuitry. Could also be the source of your height issues if that's the case.

Thanks for the quick response. I agree and suspect the accumulator pressure may be the source of the height issues.

Looking at pictures from the previous owner, the front height issue was there long before I bought the truck. Pictures show the rear was lower than the front. I didn't know enough at the time I bought it to think something was wrong if the rear was lower than the front. I just knew I could raise and lower it somewhat with the switch.

I did bleed the system soon after I bought it and got 7-8 graduations from low to high to let me know the pump is working.

Though, I have no idea of the rear globes are shot and there is an issue with the accumulator.

Let me try disconnecting the temp sensor plug under the read arrow -- courtesy of @FLtrails posting.

Disconnect AHC Fluid Temperature Sensor while reading pressures

I'm hoping you guys can help me with a few things. The FSM and posts here say to disconnect the AHC temp sensor before reading the rear pressure. It's the closest one to the firewall on the pump assembly I read on a post. Am I pointing to the correct connector in the picture below and by the way...

forum.ih8mud.com

 

[yosshaa]

did you ever get a resolution? I am installing SPC UCA's with stock AHC and am wondering where to mount the sensor on the sliding bracket... seems like lower is better.

 

[OwnerCS]

did you ever get a resolution? I am installing SPC UCA's with stock AHC and am wondering where to mount the sensor on the sliding bracket... seems like lower is better.

Good morning - So long ago. I went back and looked for pictures and didn't find anything other than what I have in the thread. Per the suggestions above, I must have bent the bracket arm away from the LCA and set the adjuster for more travel. This was happening in July (summer) of 2020. Over the next few months, I determined I had some bad globes that were affecting the ride and the rear pressure sensor was failing. By Thanksgiving, I had replaced it with Dobinsons IMS. I just remember it took several sessions in a blazing hot July garage with Techstream to get it worked out.

Good luck with the installation.

 

[Biga27110]

did you ever get a resolution? I am installing SPC UCA's with stock AHC and am wondering where to mount the sensor on the sliding bracket... seems like lower is better.

Make sure your front left to right are the same height by adjusting the torsion bars before moving sensors otherwise it wont work right.

 

[RyanGX]

Ive had the same setup and the same problems, the rear sensor will need to be adjusted it will only allow so much rake. As to the front and rear heights. The rear will always need to be higher than the front. I never could get my AHC to sit level all ways had 2ish inches higher in the rear.